1. Field of the Invention
This invention relates to respirator cartridges with particular reference to improvements in means and method for indicating end-of-service life of organic vapor/gas respirator cartridges.
2. Discussion of the Prior Art
Respirators of the type employing replaceable filter cartridges are commonly used for protection against a wide range of respiratory hazards which include toxic and disease producing dusts, mists, sprays, fumes, vapors and gases. The cartridges are replaced when their capacity to provide respiratory protection at or below hazardous concentration levels becomes apparent to the user or is otherwise arbitrarily or administratively determined.
Detection of cartridge exhaustion by a user's taste or smell of potentially hazardous fumes or gases coming through the cartridge or a resistance to his normal breathing due to clogging with dust may provide adequate protection against the danger of using spent cartridges in cases where the respiratory hazards are, for example, ammonia fumes, acidic and alkaline gases or certain dusts which produce odors, tastes and/or breathing resistances which are detectable before reaching hazardous concentrations.
Protection against organic vapors or gases which have no such warning properties, however, presents a much more serious problem which heretofore has required administrative control of cartridge use, i.e. its time of replacement being determined according to type and degree of toxicity of the hazard, its immediate concentration, the humidity at the sight and corollary environmental conditions. Variations in one or more of the aforesaid factors and their corrollaries during use of a particular cartridge can cause serious problems if not detected and, least of all, complicate end-of-service life calculations.
There are in the art a number of windowed respiratory cartridges or cannisters having color changing indicator means therewithin which allegedly afford indication of residual useful life and/or impending exhausting of the cartridges or cannisters. U.S. Pat. Nos. 1,537,519 and 3,966,440 are exemplary. These devices, however, involve the use of indicators supported by thin and/or opaque carriers such as strips of paper, activated alumina or the cartridge sorbent itself so that only the portion of the indicator against the window is visible.
The use of a porous translucent carrier for cartridge end-of-service life indicators which permits viewing thereinto for perception of a substantial depth of an indicator has been suggested in an application for patent filed January 5, 1977 and having Ser. No. 757,105, now abandoned.
While this provides an important advance in the art, i.e. by affording a more readily visible and reliable cartridge end-of-service life indication, there remains a need for still greater sensitivity to cartridge sorbent exhaustion, i.e. a more dramatic or vivid display of end-of-service life indication.
Accordingly, a principal object of this invention is to afford novel means and method for enhancing the color changing activity and general display function of gas oxidizable color indicators used in windowed or otherwise transparent respirator cartridges.
A corollary object is to enhance oxidation and color change of end-of-service life indicating means by catalytic action and/or preconditioning of vapors and gases reaching the indicating means.
Other objects and advantages of the invention will become more readily apparent from the following description.